Developers who plan to build two four-story residential buildings in place of the gas station at 25th Avenue and California Street would be subject to the Affordable Housing Bonus Program, allowing taller buildings for more below-market-rate units. (Connor Hunt/ Special to S.F. Examiner)

For nerds like me, who love how technicalities buried on page 43 of a report can shape a city for decades, and political Gordian knots, this Thursday’s Planning Commission hearing is sexier than a season finale of “Scandal.”

Back in September, Mayor Ed Lee and Supervisor Katy Tang introduced the Affordable Housing Bonus Program to offer developers bonuses of two or three extra stories in exchange for building units affordable to those earning up to 140 percent of the median income for a family of four, which is $142,000. (What about people earning $90,000? San Francisco is not for you anymore, apparently.)

ABHP targets underdeveloped areas in the Sunset, Richmond, Marina, Western Addition and a few other places. The Planning Department estimates the AHBP could get another 16,000 units built in the next 20 years.

So far so good. Lining six-story buildings down Taraval doesn’t seem like a death knell to west-side quality of life. The Sunset is a little slice of suburbia inside The City’s limits and should grow up. And what progressive wouldn’t love putting affordable housing in the Marina?

Except that there are devils in them details. Hopefully the Satans can get behind thee to fix the policy, even if it diminishes developers’ profits slightly. But will the mayor and Supervisor Tang’s chronic premature capitulation flare up again?

The proposal, as constructed, has two major problems: transit and displacement.

Decades ago, we created BART and Muni and freeways, which encourage development close to transit, as it should. While we have huge expanses of The City that look like Burlingame, there’s insufficient transit to serve a growing population. Building housing doesn’t solve the transit problem. If you build it, they may come — or they may just chill on a leaky N-Judah for three hours.

Theoretically, there could be a lot more housing built along existing transit lines, where Muni could increase service without, say, new costly subways. But we’re too busy privatizing the transit system to fund Muni.

The displacement issue arises because ABHP’s incentives, as written, apply equally to developments that displace existing rent-controlled units. Rent-controlled housing is a scarce and precious commodity, like old growth forests or a femme top, none of which are appreciated by everybody. When it’s gone, it’s gone. Anyone who can’t afford his or her rent increasing by any amount whatsoever should worry about that. It doesn’t alleviate the housing crisis to evict current residents.

Apparently, the Planning Department’s study has identified like 200 “soft sites” that could achieve the building targets without displacing tenants, like old gas stations or storefronts. That’s great, except ABHP rezones a lot of housing sites, too. And it precludes a lot of the dreaded neighborhood opposition that can slow or kill a project.

This means that without amendment, ABHP will guarantee project-by-project neighborhood slugfests over displacement and mitigation for the next 20 years.

I’m guessing the Mayor’s Office is counting on six-story projects being small enough not to attract wide opposition, and they can bulldoze existing residents, as part of turning San Francisco into the Capitol of Panem. (I’ll end up an avox soon enough.)

The neighborhoods are concerned about this and ABHP providing too much to the $120-142K demographic — and not enough to the unwashed masses toiling as teachers and artists and nonprofit workers.

There’s a happy solution: ABHP could be amended to ensure expanded transit. ABHP could either simply exclude existing housing or require one-for-one replacement of rent-controlled units, relocation and right of return. It could require an average income (say $100K) for the below-market-rate units, and let developers set their own mix around the average.

It’s a conundrum for the mayor and his board allies: There’s a political imperative to deliver more affordable housing; their donors are developers, while their voter base is the neighborhoods where said building would go down.

Who will cave first? I’m bringing popcorn and pitchforks.

Nato Green is a comedian and writer. See me go joking live at Lost Weekend Video, the Punchline, and Doc’s Lab. Holler @natogreen for details.